Electrical heating system



- June 2; 1970 F. CHR. MATH ELECTRICAL HEATING SYSTEM Filed May 1, 1967m CS United States Patent Office Patented June 2, 1970 3,515,849ELECTRICAL HEATING SYSTEM Friedrich Chr. Math, Kronberg, Taunus,Germany, assignor to Kaulfer & Co. G.m.b.H., Mainz, Germany Filed May 1,1967, Ser. No. 635,966 1 Claims priority, application Germany, Apr. 29,1966,

Int. Cl. 1165b 1/00 Us. Cl. 219-213 I 6 Claims ABSTRACT OF THEDISCLOSURE Background of the invention Electrically heatable floors areknown in various modifications, since the heating of the room throughthe floor by means of electrical energy provides for various advantages.One essential difiiculty encountered in electrical floor heating is toobtain a substantially uniform temperature over the whole area of thefloor.

Nearly all building materials used for the construction of floors, suchas for instance parquet, xylotith, polyvinylchloride, and so on, have arelatively low heat conductivity. Therefore, the portions of the floorlocated directly over the heating wire embedded therein will belocalized heated to a much higher temperature than portions adjacentthereto so that the floor surface will be divided into overheated andrelatively cold surface portions. While this difliculty may be overcomeby installing theheating wires closely adjacent to each other, such anarrangement has the disadvantage in that it requires a large amount ofheating wire material and considerable labor for installing the same sothat such a system becomes too expensive in most cases.

An additional difliculty in the construction of electrically heatablefloors or the like is that after extensive use and wear of the floor,the heating wires which are necessarily to be installed closely adjacentto the floor surface will become exposed and may cause that electricalshocks may be imparted to a person walking over the floor.

A further difficulty encountered in the construction of electricallyheated floors is that when the heating elements of the heating systemare embedded in hardenable floor material during installation, the floormaterial will shrink during hardening thereof, while the heatingelements will not shrink, so that during the hardening of the floormaterial considerable tension will be created between the floor materialand the heating elements which may lead to crack formation in the floormaterial or to {damage of the heating elements. Up to now it was notpossible to eliminate the tension thus created, and it has been onlytried to reduce the tension by using a floor material having a small aspossible shrinkage factor.

It is an object of the present invention to provide an electricalheating system for floors or the like which avoids the above-mentioneddisadvantages of electrical heating systems of this type known in theart.

It is an additional object of the present invention to to provide anelectrical heating system for floors or the like which can be easilymanufactured and installed in the floor and which will stand upperfectly under extended use.

Summary of the invention With these objects in view, the electricalheating system according to the present invention, which is adapted tobe embedded in a floor and the like, mainly comprises electrical heatingmeans distributed over a given area and arranged substantially in aplane, and grid means extending over the area and connected to theelectrical heating means but electrically insulated therefrom forprotecting the latter and for dissipating the heat developed thereby.

The grid means is preferably formed from metal and preferably the gridmeans is in the form of an electrically yieldable metal grid in form ofa wire netting or in form of perforated or punched metal sheets.

In this arrangement the portions of the metal grid which are closelyadjacent to the heating elements of the heating means will dissipate theheat developed thereby to assure a substantially uniform distribution ofthe heat over the whole surface of the floor in which the electricalheating system is embedded.

The metal grid, which when the heating system is installed will extendat least in part above the electrical heating means, will also properlyprotect the latter since during wear of the floor surface the metal gridwill be first exposed so that the heating elements located beneath themetal grid will still be properly protected. Exposure of the metal gridwill also indicate that repair of the floor surface is required.

In addition, the metal grid may be grounded to protect any personwalking on the floor from shocks, even if the insulation of the heatingelements should be damaged.

The electrical heating means of the heating system according to thepresent invention preferably comprise a plurality of elongated heatingelements arranged spaced from each other substantially in a plane and apair of conductors respectively connecting opposite ends of adjacentheating elements to each other. The heating elements are preferablyflexible and to a certain extent also stretchable, for instance each ofthe heating elements may comprise a woven band including a heating wireforming the weft thread of the band and warp threads of insulatingmaterial and insulating means covering the band, whereas the grid meansconnected to the thus constructed heating means is, as mentioned before,and elastically yieldable metal grid. If such a constructed heatingsystem is embedded in floor material which shrinks during hardening,evidently creation of tensions in the floor due to the shrinkage of thefloor material will be avoided and crack formation in the floor ordamage to the electrical heating system due to shrinkage of the floormaterial will not occur.

In a preferred form, the grid means is in form of a wire netting, thewires of which are intertwined with the elongated heating elements andthe conductors forming the electrical heating system. An electricalheating system of such a construction can be easily manufactured withautomatic machines known in the art in form of an elongated or endlessmat adapted to be cut in portions of desired length in situ so that thewhole system may be easily and quickly installed with semi-skilledlabor.

The flexible wire netting will not only prevent crack formation due toshrinkage of the floor material, but the embedded wire netting will alsoincrease the strength of the floor and reduce the danger of crackformation in the latter due to sinking of the floor foundation.

Especially advantageous results are obtained if, according to thepresent invention, a pretension is applied to' the heating means and tothe grid means of the electricalheating system before the latter isembedded into hardenable building material forming the floor and thepretension is maintained during hardening of the floor material.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a top view of the electricalheating system according to the present invention;

FIG. 2. is a cross section taken along the line II-II of FIG. 1; and

FIG. 3 is an enlarged partial view of one heating element with part ofthe insulation cut away.

Description of the preferred embodiments Referring now to the drawing,and more specifically to FIG. 1 of the same, it will be seen that theelectrical heating system according to the present invention maycomprise electrical heating means extending over a given area andarranged substantially in a plane and including heating elements 3arranged spaced from and substantially parallel to each other andconnected at opposite ends by current supply conductors 2 extendingnormal to the heating elements, and grid means which may comprise awiring netting 1, the wires of which are intertwined or interwoven withthe heating elements 3 and the conductors 2 to form with the latter aflexible heating mat. Such a mat may be produced by automatic orsemi-automatic machines in form of a more or less endless band which isthen cut in situ to the required length.

Instead of a wire mesh as shown in FIG. 1, the grid means or the metalgrid may also be formed from a perforated or grid-like stamped metalsheet extending over the electrical heating means 2, 3 and connectedthereto in any convenient manner to form therewith a flexible mat.

FIG. 2 shows a cross section taken along the line 11-11 of FIG. 1 withthe wire mesh 1 omitted.

The heating elements 3 are constructed to be not only flexible butpreferably also stretchable to a certain extent and they may comprise,as shown in FIG. 3, a heating wire 4 interwoven as a weft thread withwarp threadsS of insulating stretchable material to form therewith aflexible and stretchable band which is surrounded by an inner layer 6 ofelectrically insulating material of high heat conductivity, for instancesilicone, which in turn is surrounded by an outer insulating layer 7 ofan appropriate plastic material of relatively great mechanical strength.The cross section of the heating element 3 is preferably substantiallyoval as shown in FIG. 2. The current supply conductor 2 may beconstructed in a similar manner, of course with the cross section of thewire chosen in such a way so as to be able to carry the necessarycurrent. The wires of the current supply conductors 2 are permanentlyand electrically connected to the heating wires 4 of the heatingelements 3 at the junction of heating elements and conductors and eachjunction is insulated in a permanent and water-tight manner.

As mentioned above the electrical heating mat shown in FIG. 1 may beproduced in a more or less endless band to be cut in situ to the desiredlength. During installing of the electrical heating system according tothe present invention a pretension is preferablyapplied in a knownmanner to the mat composed of the elements 1, 2 and 3 and this heatingmat is then embedded in hardenable building material forming a floor orthe like and the pretension is maintained until the material hardens,whereby the strength of the floor will be increased by the heating matinstalled therein. Ground wires maybe connected to the wire mesh 1 sothat the latter maybe properly grounded.

It will be understood that each o f the elements de scribed above, ortwo or more together, may also find a useful application in other typesof electrical heating systems differing from the types described above.I I

While the invention has been illustrated and described as embodied in anelectrical heating systemincludin'g' electrical heating means and aflexible metal grid con- .nected thereto to form a flexible electricalheatingmat therewith, it is not intended to be limited to the detailsshown, since various modification and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can be applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standopint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. An electrical heating system adapted to be em bedded in a floor andthe like, comprising, in combina tion electrical heating meansdistributed over a given area substantially in a plane and including aplurality of main elongated heating elements arranged spaced from eachother and each comprising a narrow flat band'form'ed from a plurality ofwarp threads of insulating material all of which extend longitudinallyof the respective heating elements, a weft thread constituted by aheating wire arranged in a wavy form and extending only transverse tothe elongation of the band intertwined with said warp threads, a layerof silicone material covering said band, and a layer of insulatingmaterial covering said-layer of silicone material; a pair of elongatedconducted elements serving as conductors for said main elongated heatingelements and extending transverse to the latter and 'respectively in theregion of opposite ends thereof and respectively connecting saidopposite ends to each other; and grid means extending over said givenarea and intertwined with said main elongated heating elementsand saidelongated conductor elements so as to contact'the same over a relativelygreat area thereof, said grid means serving for protecting said elementsand for dissipating heat therefrom.

2. An electrical heating system as definedin claim 1, wherein said mainheating elements extend substantially parallel to each other and saidconductor elements extend substantially normal to said main heatingelements. h

3. An electrical heating system as defined in claim 1, wherein said gridmeans is formed from metal.

4. An electrical heating system as defined in claim 1, wherein saidconductor elements are permanently connected in a water tight and heatresistant manner to said main heating elements.

5. An electrical heating system as defined in claim 1, wherein said gridmeans comprises a Wire netting, the wires of which are intertwined withsaid main heating elements and said conductor elements.

6. An electrical heating system as defined in claim 5, wherein the wiresof said wire netting extend transverse to said elongated heatingelements.

References Cited UNITED STATES PATENTS 6 Crump 338-208 X Sutter 219-345Logan et a1. 338-214 X Price 219-549 X Custer, 219-345 Leipold et al.338-208 X Frungel 219-213 Shrimplin et al 219-213 Beery 219-213 XWilliams 219-213 Graham et a1 219-345 X US. Cl. X.R.

